<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <title>Example Page</title>
  
  <!-- 预取指定域名的DNS解析，使得后续用域名里面的东西不会进行二次解析 -->
  <link rel="dns-prefetch" href="a.com">
  <link rel="dns-prefetch" href="b.com">
  <link rel="dns-prefetch" href="c.com">
</head>
<body>
  <!-- 后续使用资源时，不会进行二次解析 -->
  <script src="a.com/index.js"></script>
  <script src="b.com/index.js"></script>
  <script src="c.com/index.js"></script>
</body>
</html>
